Drawing instrument.



A. L. MGKINSTRY. DRAWING INSTRUMENT.

APPLICATION FILED FEB.1B, 1911.

1,010,292.- Patented Nov. 28, 1 911.

COLUMBIA 'PLANOGRAPH Cu.,WAsmNu'roN, D. c.

ARTHUR L. MCKINSTRY, OF SOUTI-IBR-IDGE, MASSACHUSETTS.

' DRAWING- INSTRUMENT.

Specification of Letters Patent.

Application filed February 18, 1911.

Patented Nov. 28, 1911.

Serial No. 609,356.

T 0 all whom it may concern:

Be it known that I, ARTHUR L. Mo- KINs'rRY, citizen of the United States, residing at Southbridge, in the county of WVorcester and State of Massachusetts, have invented certain new and useful Improvements in Drawing Instruments, of which the following is a specification.

This invention comprehends certain new and useful improvements in drafting instruments or appliances, and relates particularly to an improved trammel or ellipsograph.

The invention has for its primary object a simple and eflicient construction of device of this character, the beam of which may be easily adjusted relative to the trammel blocks that move in the slots of the head block, whereby different sized ellipses may be described.

The invention has for a further object, in a device of this character, an improved construction of beam, which is provided with an extensible lead or ink point holding section, whereby the point may be easily and accurately brought to the required line. And the invention also aims to generally improve this class of devices so as to render them relatively simple and more useful and commercially desirable.

With these and other objects in view as will more fully appear as the description proceeds, the invention consists in certain constructions, arrangements and combinations of the parts that I shall hereinafter fully describe and claim.

For a full understanding of the invention, reference is to be had to the following description andv accompanying drawings, 111" which:

Figure 1 is a perspective view of an ellipsograph constructed in accordance with my invention; Fig. 2 is a sectional view thereof, parts being shown in elevation; Fig. 3 is a top plan view of the device; Fig. 4 is a detail perspective view of one of the trammel pins and blocks; and, Fig. 5 is a longitudinal sectional view of a portion of the beam.

Corresponding and like part-s are referred to in the following description and indicated in all the views of the drawings by the same reference characters.

Referring to the drawing, the numeral 1 designates the head block of my improved trammel, the same being provided with any desired number of positioning devices, there being two of these in the present instance, in the form of set screws, designated 2, working in openings 3 formed in the block, each of said set screws being provided at its inner or lower end with a pin point 4, whereby, when the set screws are adjusted in the block, these pin points may be slightly protruded from the lower face of the block and engage the drawing sheet so as to assist in holding the block in position and effectually prevent slipping.

The slots 5 of the block 1 are provided on one side with guide strips 6, secured to the upper face of the block by screws or similar fastening devices, the guide strips projecting slightly over into the slots so as to engagein grooves 7 that are formed in one side of trammel blocks 8. In the present embodiment of the invent-ion, two of these guide strips 6 are integrally joined together at their meeting ends, as best illustrated in Fig. 3.

The trammel blocks 8 are held by the guide strips 6 for a free sliding movement in the slots 5, the parts being preferably so proportioned that the blocks will be guided in the slots by the guide strips with the lower ends of the blocks in contact with the bottom of the slots.

Each of the two trammel blocks 8 is formed with a vertically disposed upwardly opening socket 9 designed to receive atrammel pin 10 which is preferably tapered at its lower end, the cylindrical body portions 11 of the trammel pins being respectively formed with transverse openings 12 to receive the beam 13 and being held on said beam at the required adjustment by set screws 11 working in the upper ends of the body portions 11 and adapted to impinge against the beam. By the arrangement of parts just described it is obvious that the beam may be easily removed, whenever desired, as the pins 10 merely fit detachably in the sockets 9 of the blocks 8.

The beam 13 carries at one end a point holding device which preferably embodies a split sleeve 15 detachably mounted in a transverse opening formed in the holder 16, the sleeve being adjustably held therein by a set screw 17 working in the outer end of the holder. The holder 16 in the present embodiment of the invention is formed with a stem 18 which fits within the tubular end 19 of the beam and which is guided therein by a gib or key 20 formed on the stem working in a slot 21 formed in the tubular end of the beam. A swivel sleeve 21 is mounted on the beam 13, and engages the gib or key 20, the sleeve working on the threaded hollow end of the beam, whereby to extend or retract the point holder, so that the point may be accurately brought to the desired line, without disturbing the adjustment of the beam relative to the trammel points. Preferably, an expansion spring 22 is mounted in the hollow threaded end of the beam 13 and pressed against the inner end of the stem 18. 1

From the foregoing description, in connection with the accompanying drawing, the operation of my improved trammel or ellipsograph will be apparent. In the practical use of the device, the device is adjusted according to the length of the or and minor axes of the ellipse to be formed, it being understood that the distance from the point, whether it be a lead point or a pin point, to the adjacent trammel point, is one-half the minor axis, and the distance from the lead or pin point to the other or farther trammel point, is one-half the major axis. Either or both axes may be changed as desired, thereby making it practical to draw any shape ellipse. When the desired adjustment has been effected, the head block 1 is placed on the board, the beam is applied to the block by the engagement of the pins 10 with the trammel blocks 8, and by placing the fingers on the sleeve 15 and turning and also slightly pressing down, the instrument will draw a perfect ellipse.

The beam 15 is preferably graduated, in any predetermined manner, and the swivel sleeve 21 is preferably bored out at one end as shown, so that it will fit over one side of the beam. Hence the distance from the central axis of the pencil point to the inner edge of the swivel sleeve being known, it is very easy to set it on the graduated beam. Preferably, the head block of the device is provided at the ends of the slots 5 with vertical lines drawn from the center of the slots downward. These can be placed upon the axes to construct an ellipse.

It is to be understood that while the foregoing description and accompanying drawing disclose what I believe to be the preferred embodiment of my invention, that the invention is not limited thereto as various changes may be made in the construction, arrangement and proportions of the parts without departing from the scope of the invention as defined in the appended claims.

Having thus described the invention, what a point holder provided with a stem working in said end and provided with a gib working in the slot of the end, and a swivel sleeve mounted on said stem and having threaded engagement with the tubular end of the beam, the sleeve engaging said gib whereby to hold the stem in position on the beam.

3. In a device of the character described, a beam provided with a tubular slotted end, a point holder provided with a stem working in said end and formed with a gib working in the slot of the end, and a sleeve mount ed on said stem and having adjustable engagement therewith,.the sleeve engaging the gib whereby to hold the stem in position on the beam.

In testimony whereof, I affix my signature in presence of two witnesses.

ARTHUR L. MCKINSTRY. [1,. 5.

Witnesses:

GEO. W. MoKINs'rRY, FRANK A. MOREY.

Copies of this patent may be obtained for five cents each, by addressing the Commissioner of Patents, Washington, D. G. 

